System and method for interference avoidance for a display device comprising an integrated sensing device

ABSTRACT

Embodiments of the invention generally provide an input device with display screens that periodically update (refresh) the screen by selectively driving electrodes corresponding to pixels in a display line. In addition to updating the display, the input device may perform capacitive sensing using the display screen as a touch area. To do this, the input device uses common electrodes for both updating the display and performing capacitive sensing, and interleaves periods of capacitive sensing between periods of updating the display lines (and pixels) based on a display frame. To avoid noise and mitigate interference during capacitive sensing, the input device may change the capacitive frame rate relative to the display frame rate based on measurements of interference. The changed capacitive frame rate may result in re-timed periods of capacitive sensing based on each display frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 13/628,040 filed on Sep. 27, 2012, entitled “SYSTEMAND METHOD FOR INTERFERENCE AVOIDANCE FOR A DISPLAY DEVICE COMPRISING ANINTEGRATED SENSING DEVICE”, which claims benefit of U.S. provisionalpatent application Ser. No. 61/683,542, filed Aug. 15, 2012 entitled“SYSTEM AND METHOD FOR INTERFERENCE AVOIDANCE FOR A DISPLAY DEVICECOMPRISING AN INTEGRATED SENSING DEVICE”, which is herein incorporatedby reference.

BACKGROUND OF THE INVENTION Field of the Invention

Embodiments of the present invention generally relate to performingcapacitance sensing while updating a display, or more specifically,modifying time periods used for capacitance sensing while updating adisplay to avoid interference and mitigate noise.

Description of Related Art

Input devices including proximity sensor devices (also commonly calledtouchpads or touch sensor devices) are widely used in a variety ofelectronic systems. A proximity sensor device typically includes asensing region, often demarked by a surface, in which the proximitysensor device determines the presence, location and/or motion of one ormore input objects. Proximity sensor devices may be used to provideinterfaces for the electronic system. For example, proximity sensordevices are often used as input devices for larger computing systems(such as opaque touchpads integrated in, or peripheral to, notebook ordesktop computers). Proximity sensor devices are also often used insmaller computing systems (such as touch screens integrated in cellularphones).

SUMMARY OF THE INVENTION

Embodiments of the invention generally provide processing system for adisplay device having an integrated capacitive sensing device. Theprocessing system includes a driver module comprising driver circuitrycoupled to a plurality of common electrodes configured to be driven fordisplay updating and capacitive sensing. The driver module is configuredto drive a first common electrode for display updating during a firstdisplay line update period of a first display frame, the first displayframe occurring at a pre-determined display frame rate, and drive asecond common electrode for display updating during a second displayline update period of the first display frame. The driver module isfurther configured to drive a first common electrode set comprising atleast one of the plurality of common electrodes for capacitive sensingat a capacitive frame rate during a first non-display period of thefirst display frame, the first non-display period occurring after thefirst display line update period and before the second display lineupdate period, and the first non-display period being at least as longas the first display line update period. The driver module is configuredto operate a second common electrode set comprising at least one of theplurality of common electrodes for interference detection during asecond non-display period. The processing system further includes areceiver module coupled to a plurality of receiver electrodes andconfigured to receive first resulting signals with the plurality ofreceiver electrodes during the first non-display period and secondresulting signals during the second non-display period. The processingsystem includes a determination module configured to determine aninterference measurement based at least in part on the second resultingsignals, wherein an amount of the first non-display period which is usedfor capacitive sensing is adjusted based on the interferencemeasurement.

Embodiments of the invention generally provide a processing system for adisplay device having an integrated capacitive sensing device. Theprocessing system includes a driver module comprising driver circuitrycoupled to a plurality of common electrodes configured to be driven fordisplay updating and capacitive sensing. The driver module is configuredto drive a first common electrode for display updating during a firstdisplay line update period of a first display frame, the first displayframe occurring at a display frame rate, and drive a second commonelectrode for display updating during a second display line updateperiod of the first display frame. The driver module is furtherconfigured to drive a first common electrode set comprising at least oneof the plurality of common electrodes for capacitive sensing during afirst non-display period at a capacitive frame rate. The firstnon-display period occurs after the first display line update period andbefore the second display line update period, and the first non-displayperiod being at least as long as the first display line update period.The driver module is configured to operate a second common electrode setcomprising at least one of the plurality of common electrodes forinterference detection during a second non-display period. Theprocessing system further includes a receiver module coupled to aplurality of receiver electrodes and configured to receive firstresulting signals with the plurality of receiver electrodes during thefirst non-display period and second resulting signals during the secondnon-display period. The processing system includes a determinationmodule configured to determine an interference measurement based atleast in part on the second resulting signals, wherein the determinationmodule is further configured to adjust an amount of capacitive framesper display frame based on the interference measurement.

Embodiments of the invention may further provide a method for operatinga display device having an integrated capacitive sensing device. Themethod includes driving, a first common electrode of a plurality ofcommon electrodes for display updating during a first display lineupdate period of a first display frame, the first display frameoccurring at a display frame rate, wherein the plurality of commonelectrodes are configured for display updating and capacitive sensing,and driving a second common electrode of the plurality of commonelectrodes for display updating during a second display line updateperiod of the first display frame. The method further includes operatinga first common electrode set comprising at least one of the plurality ofcommon electrodes for interference detection, and receiving firstresulting signals from a plurality of receiver electrodes whileoperating the first common electrode set for interference detection. Themethod includes determining an interference measurement based at leastin part on the first resulting signals, adjusting an amount of a firstnon-display period which is used for capacitive sensing based on theinterference measurement. The method further includes driving a secondfirst common electrode set comprising at least one of the plurality ofcommon electrodes for capacitive sensing during the amount of the firstnon-display period of the first display frame at a capacitive framerate. The first non-display period may occur after the first displayline update period and before the second display line update period, andthe first non-display period is at least as long as the first displayline update period.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic block diagram of an exemplary display deviceintegrated with an input device, according to an embodiment describedherein.

FIG. 2 illustrates a stack-up of a sensor assembly that may be used inthe input device to sense the input object, according to an embodimentdescribed herein.

FIG. 3 is a timing chart for processing a display frame with interleavedcapacitive sensing periods, according to one embodiment disclosedherein.

FIG. 4 is a timing diagram for interleaving a capacitive sensing periodinto a display frame update, according to one embodiment disclosedherein.

FIG. 5 illustrates a system for communicating between an electronicsystem and an input device that dynamically changes a capacitive framerate relative to a display frame rate, according to one embodimentdisclosed herein.

FIG. 6 illustrates a flow diagram of a method of mitigating noise bymodifying periods of capacitance sensing with display updating,according to an embodiment disclosed herein.

FIG. 7 is a timing chart for processing a display frame with interleavedcapacitive sensing periods, according to one embodiment disclosedherein.

FIGS. 8A-8B are timing charts for processing a display frame withinterleaved capacitive sensing periods, according to one embodimentdisclosed herein.

FIG. 9 is a timing chart for processing a display frame with interleavedcapacitive sensing periods, according to one embodiment disclosedherein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation. The drawings referred to here should not beunderstood as being drawn to scale unless specifically noted. Also, thedrawings are often simplified and details or components omitted forclarity of presentation and explanation. The drawings and discussionserve to explain principles discussed below, where like designationsdenote like elements.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, brief summary or the following detailed description.

Various embodiments of the present technology provide input devices andmethods for improving usability. Input devices with display screensperiodically update (refresh) the screen by selectively drivingelectrodes corresponding to pixels in the screen's display lines. Ingeneral, the input devices drive each electrode until each display line(and each pixel) of a display frame is updated. As used herein, adisplay frame includes the necessary information for updating, at leastonce, a defined portion of the display lines in a display screen. Forexample, if the input device updates the display screen sixty times asecond, the input device receives sixty display frames which the inputdevice uses to update each display line sixty times. Moreover, a displayframe may not include all the display lines in the display screen. Forexample, only a portion of the display screen may be actively displayingan image, and thus, the display frames may contain only the data neededto update the display lines in the active portion.

In addition to updating the display, the input device may performcapacitive sensing using the display screen as a touch area. Moreover,the input device may interleave periods of capacitive sensing betweenperiods of updating the display based on a display frame. For example,the input device may update the first half of the display lines of thedisplay screen, pause display updating, perform capacitive sensing, andfinish updating the rest of the display lines. In this manner, the timeperiod necessary for updating a screen based on a single display frameincludes one or more interleaved periods of capacitive sensing. Furtherstill, the input device may use common electrodes for both updating thedisplay and performing capacitive sensing.

In one embodiment, the periods of capacitive sensing may be dynamicallyvaried to avoid interference and mitigate noise at the input device. Forexample, the input device may modify the amount of the interleavedperiods used for capacitive sensing, modify the timing of interleavedperiods relative to each display frame, or some combination thereof,based on detected interference. Increasing the amount of the interleavedperiods used for capacitive sensing enables the input device to increasea range of sensing frequencies for more effective frequency hopping.Further, modifying the timing of interleaved periods relative to eachdisplay frame enables the input device to increase a number ofcapacitive measurements acquired during capacitive sensing for narrowerfilter bandwidths used in interference filtering.

FIG. 1 is a block diagram of an exemplary input device 100, inaccordance with embodiments of the present technology. In oneembodiment, input device 100 comprises a display device having anintegrated sensing device. Although embodiments of the presentdisclosure may be utilized in a display device integrated with a sensingdevice, it is contemplated that the invention may be embodied in displaydevices without integrated input devices. The input device 100 may beconfigured to provide input to an electronic system 150. As used in thisdocument, the term “electronic system” (or “electronic device”) broadlyrefers to any system capable of electronically processing information.Some non-limiting examples of electronic systems 150 include personalcomputers of all sizes and shapes, such as desktop computers, laptopcomputers, netbook computers, tablets, web browsers, e-book readers, andpersonal digital assistants (PDAs). Additional example electronicsystems 150 include composite input devices, such as physical keyboardsthat include input device 100 and separate joysticks or key switches.Further example electronic systems 150 include peripherals such as datainput devices (including remote controls and mice), and data outputdevices (including display screens and printers). Other examples includeremote terminals, kiosks, and video game machines (e.g., video gameconsoles, portable gaming devices, and the like). Other examples includecommunication devices (including cellular phones, such as smart phones),and media devices (including recorders, editors, and players such astelevisions, set-top boxes, music players, digital photo frames, anddigital cameras). Additionally, the electronic system could be a host ora slave to the input device.

The input device 100 can be implemented as a physical part of theelectronic system 150, or can be physically separate from the electronicsystem 150. As appropriate, the input device 100 may communicate withparts of the electronic system using any one or more of the following:buses, networks, and other wired or wireless interconnections. Examplesinclude I²C, SPI, PS/2, Universal Serial Bus (USB), Bluetooth, RF, andIRDA.

In FIG. 1, the input device 100 is shown as a proximity sensor device(also often referred to as a “touchpad” or a “touch sensor device”)configured to sense input provided by one or more input objects 140 in asensing region 120. Example input objects include fingers and styli, asshown in FIG. 1.

Sensing region 120 encompasses any space above, around, in and/or nearthe input device 100 in which the input device 100 is able to detectuser input (e.g., user input provided by one or more input objects 140).The sizes, shapes, and locations of particular sensing regions may varywidely from embodiment to embodiment. In some embodiments, the sensingregion 120 extends from a surface of the input device 100 in one or moredirections into space until signal-to-noise ratios prevent sufficientlyaccurate object detection. The distance to which this sensing region 120extends in a particular direction, in various embodiments, may be on theorder of less than a millimeter, millimeters, centimeters, or more, andmay vary significantly with the type of sensing technology used and theaccuracy desired. Thus, some embodiments sense input that comprises nocontact with any surfaces of the input device 100, contact with an inputsurface (e.g., a touch surface) of the input device 100, contact with aninput surface of the input device 100 coupled with some amount ofapplied force or pressure, and/or a combination thereof. In variousembodiments, input surfaces may be provided by surfaces of casingswithin which the sensor electrodes reside, by face sheets applied overthe sensor electrodes or any casings, etc. In some embodiments, thesensing region 120 has a rectangular shape when projected onto an inputsurface of the input device 100.

The input device 100 may utilize any combination of sensor componentsand sensing technologies to detect user input in the sensing region 120.The input device 100 comprises one or more sensing elements 121 fordetecting user input. As several non-limiting examples, the input device100 may use capacitive, elastive, resistive, inductive, magneticacoustic, ultrasonic, and/or optical techniques.

Some implementations are configured to provide images that span one,two, three, or higher dimensional spaces. Some implementations areconfigured to provide projections of input along particular axes orplanes.

In some resistive implementations of the input device 100, a flexibleand conductive first layer is separated by one or more spacer elementsfrom a conductive second layer. During operation, one or more voltagegradients are created across the layers. Pressing the flexible firstlayer may deflect it sufficiently to create electrical contact betweenthe layers, resulting in voltage outputs reflective of the point(s) ofcontact between the layers. These voltage outputs may be used todetermine positional information.

In some inductive implementations of the input device 100, one or moresensing elements 121 pick up loop currents induced by a resonating coilor pair of coils. Some combination of the magnitude, phase, andfrequency of the currents may then be used to determine positionalinformation.

In some capacitive implementations of the input device 100, voltage orcurrent is applied to create an electric field. Nearby input objectscause changes in the electric field, and produce detectable changes incapacitive coupling that may be detected as changes in voltage, current,or the like.

Some capacitive implementations utilize arrays or other regular orirregular patterns of capacitive sensing elements 121 to create electricfields. In some capacitive implementations, separate sensing elements121 may be ohmically shorted together to form larger sensor electrodes.Some capacitive implementations utilize resistive sheets, which may beuniformly resistive.

Some capacitive implementations utilize “self capacitance” (or “absolutecapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes and an input object. In variousembodiments, an input object near the sensor electrodes alters theelectric field near the sensor electrodes, thus changing the measuredcapacitive coupling. In one implementation, an absolute capacitancesensing method operates by modulating sensor electrodes with respect toa reference voltage (e.g., system ground), and by detecting thecapacitive coupling between the sensor electrodes and input objects.

Some capacitive implementations utilize “mutual capacitance” (or“transcapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes. In various embodiments, an inputobject near the sensor electrodes alters the electric field between thesensor electrodes, thus changing the measured capacitive coupling. Inone implementation, a transcapacitive sensing method operates bydetecting the capacitive coupling between one or more transmitter sensorelectrodes (also “transmitter electrodes” or “transmitters”) and one ormore receiver sensor electrodes (also “receiver electrodes” or“receivers”). Transmitter sensor electrodes may be modulated relative toa reference voltage (e.g., system ground) to transmit transmittersignals. Receiver sensor electrodes may be held substantially constantrelative to the reference voltage to facilitate receipt of resultingsignals. A resulting signal may comprise effect(s) corresponding to oneor more transmitter signals, and/or to one or more sources ofenvironmental interference (e.g., other electromagnetic signals). Sensorelectrodes may be dedicated transmitters or receivers, or may beconfigured to both transmit and receive.

In FIG. 1, a processing system 110 is shown as part of the input device100. The processing system 110 is configured to operate the hardware ofthe input device 100 to detect input in the sensing region 120. Theprocessing system 110 comprises parts of or all of one or moreintegrated circuits (ICs) and/or other circuitry components. (Forexample, a processing system for a mutual capacitance sensor device maycomprise transmitter circuitry configured to transmit signals withtransmitter sensor electrodes, and/or receiver circuitry configured toreceive signals with receiver sensor electrodes). In some embodiments,the processing system 110 also comprises electronically-readableinstructions, such as firmware code, software code, and/or the like. Insome embodiments, components composing the processing system 110 arelocated together, such as near sensing element(s) of the input device100. In other embodiments, components of processing system 110 arephysically separate with one or more components close to sensingelement(s) of input device 100, and one or more components elsewhere.For example, the input device 100 may be a peripheral coupled to adesktop computer, and the processing system 110 may comprise softwareconfigured to run on a central processing unit of the desktop computerand one or more ICs (perhaps with associated firmware) separate from thecentral processing unit. As another example, the input device 100 may bephysically integrated in a phone, and the processing system 110 maycomprise circuits and firmware that are part of a main processor of thephone. In some embodiments, the processing system 110 is dedicated toimplementing the input device 100. In other embodiments, the processingsystem 110 also performs other functions, such as operating displayscreens, driving haptic actuators, etc.

The processing system 110 may be implemented as a set of modules thathandle different functions of the processing system 110. Each module maycomprise circuitry that is a part of the processing system 110,firmware, software, or a combination thereof. In various embodiments,different combinations of modules may be used. Example modules includehardware operation modules for operating hardware such as sensorelectrodes and display screens, data processing modules for processingdata such as sensor signals and positional information, and reportingmodules for reporting information. Further example modules includesensor operation modules configured to operate sensing element(s) todetect input, identification modules configured to identify gesturessuch as mode changing gestures, and mode changing modules for changingoperation modes.

In one embodiment, the processing system 110 includes a driver modulehaving driver circuitry and configured to drive hardware components forcapacitive sensing, display updating, and interference measurement. Insome embodiments, the processing system 110 may include a receivermodule configured to process resulting signals for capacitive sensing,and a determination module configured to adjust a process for capacitivesensing based at least in part on interference measurements.

In some embodiments, the processing system 110 responds to user input(or lack of user input) in the sensing region 120 directly by causingone or more actions. Example actions include changing operation modes,as well as GUI actions such as cursor movement, selection, menunavigation, and other functions. In some embodiments, the processingsystem 110 provides information about the input (or lack of input) tosome part of the electronic system (e.g., to a central processing systemof the electronic system that is separate from the processing system110, if such a separate central processing system exists). In someembodiments, some part of the electronic system processes informationreceived from the processing system 110 to act on user input, such as tofacilitate a full range of actions, including mode changing actions andGUI actions.

For example, in some embodiments, the processing system 110 operates thesensing element(s) of the input device 100 to produce electrical signalsindicative of input (or lack of input) in the sensing region 120. Theprocessing system 110 may perform any appropriate amount of processingon the electrical signals in producing the information provided to theelectronic system. For example, the processing system 110 may digitizeanalog electrical signals obtained from the sensor electrodes. Asanother example, the processing system 110 may perform filtering orother signal conditioning. As yet another example, the processing system110 may subtract or otherwise account for a baseline, such that theinformation reflects a difference between the electrical signals and thebaseline. As yet further examples, the processing system 110 maydetermine positional information, recognize inputs as commands,recognize handwriting, and the like.

“Positional information” as used herein broadly encompasses absoluteposition, relative position, velocity, acceleration, and other types ofspatial information. Exemplary “zero-dimensional” positional informationincludes near/far or contact/no contact information. Exemplary“one-dimensional” positional information includes positions along anaxis. Exemplary “two-dimensional” positional information includesmotions in a plane. Exemplary “three-dimensional” positional informationincludes instantaneous or average velocities in space. Further examplesinclude other representations of spatial information. Historical dataregarding one or more types of positional information may also bedetermined and/or stored, including, for example, historical data thattracks position, motion, or instantaneous velocity over time.

In some embodiments, the input device 100 is implemented with additionalinput components that are operated by the processing system 110 or bysome other processing system. These additional input components mayprovide redundant functionality for input in the sensing region 120, orsome other functionality. FIG. 1 shows buttons 130 near the sensingregion 120 that can be used to facilitate selection of items using theinput device 100. Other types of additional input components includesliders, balls, wheels, switches, and the like. Conversely, in someembodiments, the input device 100 may be implemented with no other inputcomponents.

In some embodiments, the input device 100 comprises a touch screeninterface, and the sensing region 120 overlaps at least part of anactive area of a display screen of the display device. For example, theinput device 100 may comprise substantially transparent sensorelectrodes overlaying the display screen and provide a touch screeninterface for the associated electronic system. The display screen maybe any type of dynamic display capable of displaying a visual interfaceto a user, and may include any type of light emitting diode (LED),organic LED (OLED), cathode ray tube (CRT), liquid crystal display(LCD), plasma, electroluminescence (EL), or other display technology.The input device 100 and the display device may share physical elements.For example, some embodiments may utilize some of the same electricalcomponents for displaying and sensing. As another example, the displaydevice may be operated in part or in total by the processing system 110.

It should be understood that while many embodiments of the presenttechnology are described in the context of a fully functioningapparatus, the mechanisms of the present technology are capable of beingdistributed as a program product (e.g., software) in a variety of forms.For example, the mechanisms of the present technology may be implementedand distributed as a software program on information bearing media thatare readable by electronic processors (e.g., non-transitorycomputer-readable and/or recordable/writable information bearing mediareadable by the processing system 110). Additionally, the embodiments ofthe present technology apply equally regardless of the particular typeof medium used to carry out the distribution. Examples ofnon-transitory, electronically readable media include various discs,memory sticks, memory cards, memory modules, and the like.Electronically readable media may be based on flash, optical, magnetic,holographic, or any other storage technology.

FIG. 2 shows a portion of an exemplary pattern of sensing elements 121configured to sense in a sensing region associated with the pattern,according to some embodiments. For clarity of illustration anddescription, FIG. 2 shows the sensing elements 121 in a pattern ofsimple rectangles, and does not show various components. This pattern ofsensing elements 121 comprises a plurality of transmitter electrodes 160(160-1, 160-2, 160-3, . . . 160-n), and a plurality of receiverelectrodes 170 (170-1, 170-2, 170-3, . . . 170-n) disposed over theplurality of transmitter electrodes 160.

Transmitter electrodes 160 and receiver electrodes 170 are typicallyohmically isolated from each other. That is, one or more insulatorsseparate transmitter electrodes 160 and receiver electrodes 170 andprevent them from electrically shorting to each other. In someembodiments, transmitter electrodes 160 and receiver electrodes 170 areseparated by insulative material disposed between them at cross-overareas; in such constructions, the transmitter electrodes 160 and/orreceiver electrodes 170 may be formed with jumpers connecting differentportions of the same electrode. In some embodiments, transmitterelectrodes 160 and receiver electrodes 170 are separated by one or morelayers of insulative material. In some other embodiments, transmitterelectrodes 160 and receiver electrodes 170 are separated by one or moresubstrates; for example, they may be disposed on opposite sides of thesame substrate, or on different substrates that are laminated together.

The areas of localized capacitive coupling between transmitterelectrodes 160 and receiver electrodes 170 may be termed “capacitivepixels.” The capacitive coupling between the transmitter electrodes 160and receiver electrodes 170 change with the proximity and motion ofinput objects in the sensing region associated with the transmitterelectrodes 160 and receiver electrodes 170.

In some embodiments, the sensor pattern is “scanned” to determine thesecapacitive couplings. That is, the transmitter electrodes 160 are drivento transmit transmitter signals. Transmitters may be operated such thatone transmitter electrode transmits at one time, or multiple transmitterelectrodes transmit at the same time. Where multiple transmitterelectrodes transmit simultaneously, these multiple transmitterelectrodes may transmit the same transmitter signal and effectivelyproduce an effectively larger transmitter electrode, or these multipletransmitter electrodes may transmit different transmitter signals. Forexample, multiple transmitter electrodes may transmit differenttransmitter signals according to one or more coding schemes that enabletheir combined effects on the resulting signals of receiver electrodes170 to be independently determined.

The receiver sensor electrodes 170 may be operated singly or multiply toacquire resulting signals. The resulting signals may be used todetermine measurements of the capacitive couplings at the capacitivepixels.

A set of measurements from the capacitive pixels form a “capacitiveimage” (also “capacitive frame”) representative of the capacitivecouplings at the pixels. Multiple capacitive images may be acquired overmultiple time periods, and differences between them used to deriveinformation about input in the sensing region. For example, successivecapacitive images acquired over successive periods of time can be usedto track the motion(s) of one or more input objects entering, exiting,and within the sensing region.

The background capacitance of a sensor device is the capacitive imageassociated with no input object in the sensing region. The backgroundcapacitance changes with the environment and operating conditions, andmay be estimated in various ways. For example, some embodiments take“baseline images” when no input object is determined to be in thesensing region, and use those baseline images as estimates of theirbackground capacitances.

Capacitive images can be adjusted for the background capacitance of thesensor device for more efficient processing. Some embodiments accomplishthis by “baselining” measurements of the capacitive couplings at thecapacitive pixels to produce a “baselined capacitive image.” That is,some embodiments compare the measurements forming a capacitance imagewith appropriate “baseline values” of a “baseline image” associated withthose pixels, and determine changes from that baseline image.

In some touch screen embodiments, transmitter electrodes 160 compriseone or more common electrodes (e.g., “V-com electrode”) used in updatingthe display of the display screen. These common electrodes may bedisposed on an appropriate display screen substrate. For example, thecommon electrodes may be disposed on the TFT glass in some displayscreens (e.g., In Plane Switching (IPS) or Plane to Line Switching(PLS)), on the bottom of the color filter glass of some display screens(e.g., Patterned Vertical Alignment (PVA) or Multi-domain VerticalAlignment (MVA)), coupled to one end of an organic light emitting diode(OLED) etc. In such embodiments, the common electrode can also bereferred to as a “combination electrode”, since it performs multiplefunctions. In various embodiments, each transmitter electrode 160comprises one or more common electrodes. In other embodiments, at leasttwo transmitter electrodes 160 may share at least one common electrode.

In various touch screen embodiments, the “capacitive frame rate” (therate at which successive capacitive images are acquired) may be the sameor be different from that of the “display frame rate” (the rate at whichthe display image is updated, including refreshing the screen toredisplay the same image). In some embodiments where the two ratesdiffer, successive capacitive images are acquired at different displayupdating states, and the different display updating states may affectthe capacitive images that are acquired. That is, display updatingaffects, in particular, the background capacitive image. Thus, if afirst capacitive image is acquired when the display updating is at afirst state, and a second capacitive image is acquired when the displayupdating is at a second state, the first and second capacitive imagesmay differ due to differences in the background capacitive imageassociated with the display updating states, and not due to changes inthe sensing region. This is more likely where the capacitive sensing anddisplay updating electrodes are in close proximity to each other, orwhen they are shared (e.g., combination electrodes).

In one embodiment, the capacitive frame rate may be set relative to thedisplay frame rate. In one embodiments, the capacitive frame rate may bean integer multiple (e.g., “2×”, “1×”) of the display frame rate. Inother embodiments, the capacitive frame rate is a fractional multiple(e.g., “1.5×”) of the display frame rate. In yet further embodiments,the capacitive frame rate may be any fraction or integer of the displayframe rate. By way of example, a capacitive frame rate that isconfigured as “2×” of a display frame rate of 60 Hz would have a rate of120 Hz. Similarly, a capacitive frame rate that is configured as “1.5×”would have a rate of 90 Hz.

For convenience of explanation, a capacitive image that is taken duringa particular display updating state is considered to be of a particularframe type. That is, a particular frame type is associated with amapping of a particular capacitive sensing sequence with a particulardisplay sequence. Thus, a first capacitive image taken during a firstdisplay updating state is considered to be of a first frame type, asecond capacitive image taken during a second display updating state isconsidered to be of a second frame type, a third capacitive image takenduring a first display updating state is considered to be of a thirdframe type, and so on. Where the relationship of display update stateand capacitive image acquisition is periodic, capacitive images acquiredcycle through the frame types and then repeats. In some embodiments,there may be “n” capacitive images for every display updating state.

Performing Capacitive Sensing Between Display Line Updates

A common electrode may be configured to transmit signals for displayupdating during the pixel update period. In one embodiment, each commonelectrode of a plurality of common electrodes sequentially transmitssignals for display updating. In various embodiments, multiple commonelectrodes may transmit signals for capacitive sensing during anon-display update period. In one embodiment, the non-display updateperiod comprises at least one of a horizontal blanking period, anin-frame blanking period and a vertical blanking period, as shown ingreater detail in FIG. 3.

FIG. 3 is a timing chart 300 for processing a display frame withinterleaved capacitive sensing periods, according to one embodimentdisclosed herein. Specifically, the timing chart 300 illustrates thedifferent time periods in a display frame. As shown, different timeperiods are designated during which common electrodes 0-N maysequentially transmit signals for display updating during acorresponding “pixel update” period in the display frame. Time periodsA-D, F-H each represent the time used to update a single display line ofa display screen in the input device, such as the input device 100. Thisdisplay line update time is further divided into a time period 310 usedto update the pixels of the display line and a buffer time, alsoreferred to as a horizontal blanking period 315, that occurs betweeneach display line update 305. The driver module may use the horizontalblanking period 315 to, for example, retrieve data needed to update thenext display line, drive a voltage onto the common electrode(s)corresponding to the display line, or allow signals to settle to reduceinterference when updating subsequent display lines. Nonetheless, theembodiments disclosed herein are not limited to an input device with ahorizontal blanking period 315 and may be used in a system where thereis no buffer time between the pixel update period 310 and the nextdisplay line update 305. In various embodiments, the horizontal blankingperiod 315 is reduced in length such that it is substantiallynon-existent. In other embodiments, the horizontal blanking period 315is reduced in length such that it is no longer than the time needed toconfigure a common electrode to update a display line.

Moreover, the common electrodes 0-N may be driven to update pixels ofthe display frame in any order. For example, the driver module mayupdate a display line at the top of the display screen, and in thesubsequent display line update 305, update a display line at the bottomof the screen. As a result, the input device may sequentially drive twocommon electrodes that are not located sequentially in the displayscreen. Further still, a display frame may not update each display lineof the display screen if, for example, only a portion of the displayscreen is actively displaying information. Thus, the common electrodes0-N in chart 300 may represent only a portion of the common electrodesin the input device.

In one embodiment, the time period E represents the time for capacitivesensing, or a capacitive sensing period. Time Period E may be at leastas long as the time to update a single line of the display screen. Inanother embodiment, time period E is longer than the time to update asingle line of a display screen. Moreover, the input device may use thesame common electrodes used to update the pixels of the display screento drive transmitter signals. That is, the common electrodes may servedual purposes. During a display update period, a common electrodeupdates the pixels in the display, but during a capacitive sensingperiod, the common electrodes are used as transmitter electrodes.

In one embodiment, after updating display lines during time periods A-D,the driver module may pause display updating and use time period E toperform capacitive sensing. During this time period, the driver modulemay not update any of the pixels in the display screen. Rather, thedriver module may transmit transmitter signals on transmitter electrodes(e.g., one or more common electrodes) in the display screen. Based onthe resulting signals received by the receiver electrodes 170, the inputdevice derives positional information of an input object proximate to atouch sensitive area of the device.

In one embodiment, the driver module may pause updating the display inorder to perform capacitance sensing. As shown in chart 300, the drivermodule updates the pixels associated with common electrodes 0-3 duringtime periods A-D. However, at time period E, display updating is paused(i.e., the driver module does not continue to update the next displayline in the frame) while capacitive sensing is performed. Specifically,the capacitive sensing periods are interleaved with the display lineupdates of the display frame. Accordingly, the capacitive sensing period320 is also referred to interchangeably as a long horizontal blankingperiod (long h-period), distributed vertical blanking period, or anin-frame blanking period, where display updating is paused while thedriver module performs capacitive sensing prior to completion of displayupdating of an entire display frame. The driver module resumes displayupdating for the same display frame after the capacitive sensing period320 is completed.

As shown in FIG. 3, the capacitive sensing periods 320 occur betweengroups of pixel update periods 310 of a display frame. In oneembodiment, the capacitive sensing periods 320 are longer than thehorizontal blanking periods 315 and, in some embodiments, are at leastas long as a pixel update period 310 or the display line update 305.Stated differently, the driver module may perform capacitance sensingduring the entire time period E which includes the capacitive sensingperiod 320 that is at least as long as a pixel update period 310 and ahorizontal blanking period 315. As shown, time period E is three timesas long (as shown by the horizontal and vertical arrows) as other timeperiods in chart 300—i.e., time periods A-D and F-H. However, theduration of the capacitive sensing periods 320 may be adjusted accordingto the particular design of the input device.

Allowing the capacitive sensing to occur during the capacitive sensingperiod 320 may allow the input device to measure accurately the changein capacitance for the selected electrodes (i.e., electrodes driving thetransmitter signal) without interruption. Accordingly, performingcapacitive sensing during an capacitive sensing period 320 is referredto herein as contiguous capacitive sensing since change in capacitivecoupling is measured for a selected electrode or group of electrodes ina continuous time period.

Furthermore, the driver module may perform capacitive sensing using theelectrodes that were used in the previous display update period. Forexample, during time period E, the driver module may transmit atransmitter signal simultaneously on common electrodes 0-3. In thismanner, the driver module may use one or more common electrodes toupdate the pixels in a display line and, before continuing to update theother display lines in the display frame, perform capacitive sensingusing those same electrodes.

When display updating is paused, the driver module may still drivesignals on the common electrodes that are not transmitting thetransmitter signal. For example, while the transmitter signal istransmitted on one or more electrodes, the driver module may apply areference voltage (or another other signal) to other common electrodesin the display screen. Fixing the common electrodes currently not beingused for capacitive sensing to a reference voltage may improve theability of the input device to derive accurate positional informationfor the input object. Thus, when display updating is paused, the drivermodule may cease to update the pixels in the display screen but stilluse the common electrodes for capacitive sensing.

The vertical blanking period 325 is the period between the last displayline update period of a display frame and the beginning of a displayline update period in a subsequent display frame. Although not shown inFIG. 3, the timing chart 300 may also include a second vertical blankingperiod at the beginning of updating a display based on a receiveddisplay frame—i.e., before time period A. Because the input device doesnot update the display during these vertical blanking periods 325, insome embodiments, the driver module may also use either the first or thesecond vertical blanking periods (or both) to perform capacitancesensing. Similar to the capacitive sensing period 320, the verticalblanking periods 325 facilitate contiguous capacitive sensing since bothof these blanking periods may provide a sufficient length of time tomeasure the change in capacitance associated with a selected commonelectrode without significant interruptions. However, the verticalblanking period 325 is distinguished from the capacitive sensing period320 since this period 325 falls before or after all of the display linesof the display frame have been updated, while the capacitive sensingperiod 320 is inserted between display line updates 305 of the samedisplay frame. For example, as shown in FIG. 3, a capacitive sensingperiod 320 (e.g., during time period E) occurs after a common electrode3 transmits signals for display updating (e.g., during time period D)and before common electrode 4 transmits signals for display updating(e.g., during time period F).

In many embodiments, the length of a horizontal blanking period 315,capacitive sensing period 320 and/or a vertical blanking period 325 maybe changed. However, the display frame rate may be fixed. Therefore, asthe length of one of these non-display update periods is changed, atleast one of the other non-display update periods may also change sothat the length of the display frame does not change. For example, in anembodiment where a capacitive sensing period 320 is included within thedisplay frame, the duration of the horizontal blanking periods 315and/or the vertical blanking period 325 may be decreasedcorrespondingly. By reducing the horizontal blanking periods 315corresponding to the display line update periods 305 of a first set ofcommon electrodes, a capacitive sensing period 320 may be insertedwithin a display frame. For example, the length of the horizontalblanking periods 315 may be reduced such that a capacitive sensingperiod 320 is at least as long as a pixel update period 310, oralternatively, is longer than the pixel update period 310. Given that ahorizontal blanking period 315 is “T” μs long, reducing the horizontalblanking period 315 by about “N” ps for “M” corresponding commonelectrodes results in an capacitive sensing period 320 of length“(T−N)*M” ps being created. The duration of a capacitive sensing period320 may be based on a sum of the reduction of each horizontal blankingperiod 315. In other embodiments, the duration of the capacitive sensingperiod 320 may be based on changing the vertical blanking period 325, orbased on changing both the horizontal blanking periods 315 and thevertical blanking period 325. The duration of a capacitive sensingperiod 320 may be set according to, for example, the amount of timerequired to perform contiguous capacitive sensing for a correspondinggroup of common electrodes. For example, for a group of commonelectrodes, 100 ps may be needed for contiguous capacitive sensing.Therefore, a corresponding capacitive sensing period 320 is determinedto be at least 100 ps in length. To free up 100 ps but still maintainthe desired frame rate, one or more of the horizontal blanking periods315 or the vertical blanking period 325 may be reduced.

In one embodiment, the duration and occurrence of the in-frame blankingperiod(s) 320 may be set to mitigate noise from switching betweencapacitive sensing and display updating, or to perform frequency hoppingto reduce noise interference. In some embodiments, a change in thecapacitive frame rate relative to the display frame rate based oninterference measurements may result in a re-timing of the capacitivesensing periods 320. For example, to change a capacitive frame rate from2× to 1× the display frame rate (which is typically about 60 Hz), one ormore capacitive sensing periods 320 may be increased from being equal toa pixel update period 310 to being longer than (e.g., twice) a pixelupdate period 310. In this example, one or more capacitive sensingperiods 320 may be re-timed to occur once per display frame rather thantwice per display frame.

Even though FIG. 3 was described in an embodiment where commonelectrodes 0-N are used for both updating a display and performingcapacitive sensing, this disclosure is not limited to such. In oneembodiment, the input device may use in-frame blanking periods toperform capacitive sensing even if the transmitter signals aretransmitted on electrodes that are not used when updating the display.In other embodiments, the transmitter electrodes may be separate fromthe common electrodes. Because the electrodes used for display updatingand the electrodes used for capacitive sensing may be in close proximityin the input device, performing the two functions in mutually exclusivetime periods may reduce the amount of electrical interference betweenthe different electrode sets.

FIG. 4 is a timing diagram for interleaving a capacitive sensing periodinto a display frame update, according to one embodiment disclosedherein. The timing diagram 400 includes the waveforms propagated oncommon electrodes 0-5 during the time periods A-F shown in FIG. 3. Inthe embodiment shown, the horizontal blanking periods 315 of the displayline update 305 have been set to 0 and omitted from FIG. 4 for clarityof illustration.

During time periods A-D, the driver module activates, i.e., drives asignal onto, one of the common electrodes and updates the pixelsassociated with the corresponding display line. While one electrode isactivated, the other electrodes may be kept at a constant voltage.Moreover, the common electrodes may not switch instantaneously at eachtime period as shown (e.g., electrode 0 switches off as electrode 1switches on). Instead, there may be some delay—e.g., the horizontalblanking period—where the electrodes ramp up or ramp down. In variousembodiments, one or more common electrode may be activated in anoverlapping manner, such that at least two common electrodes areactivated during the time period. For example, common electrode 0 andcommon electrode 1 may both be activated during overlapping portions ofTime Period A.

During time period E, the driver module pauses display updating andswitches to capacitive sensing. In FIG. 4, the common electrodes 0-3 aregrouped into a transmitter electrode block (e.g., transmitter electrode170 ₁) where a transmitter signal (e.g., square wave) is transmittedsimultaneously on each common electrode assigned to the block. Forexample, a display device may include hundreds of common electrodes but,when performing capacitance sensing, the device may segment the commonelectrodes into blocks of transmitter electrodes (e.g., around 20transmitter electrodes of 40 common electrodes each) where each block istreated as a single transmission electrode. For simplicity, FIG. 4illustrates an embodiment where common electrodes 0-3 are assigned to atransmitter electrode and are each driven with the same transmittersignal. Alternatively, in other display devices, the common electrodesmay be a single electrode “plane” made up of a plurality of electrodesegments are driven to a same reference voltage during display updating.During capacitive sensing however, the different electrode segments(i.e., transmitter electrodes) of the electrode plane are used totransmit the transmitter signals at different times. Further, in otherembodiments, during Time Period E, one or more common electrodes may beoperated for interference sensing. In such embodiments, operating theone or more common electrodes for interference sensing comprises drivingthe one or more common electrodes with a substantially constant voltagesignal or electrically floating the one or more common electrodes.

The capacitance sensing period may further be divided into a pluralityof sensing cycles 410 (or touch cycles). Advantageously, using anin-frame blanking period may permit the driver module to drive aplurality of contiguous sensing cycles sufficient for deriving a changein capacitance between the electrode block and one or more receiverelectrodes. For example, assuming the input device performs six sensingcycles 410 in order to accurately measure the change of capacitance butcan only perform two sensing cycles 410 during a horizontal blankingperiod 315, the driver module must use at least three horizontalblanking periods 315 for each electrode block. Conversely, with thecapacitive sensing period 320 shown in FIG. 4, the much longer length ofthe capacitive sensing period 320 allows the input device to measure thesix sensing cycles 410 contiguously without updating the display betweenthe sensing cycles 410.

Of course, the input device may be configured to perform more or lessthan six cycles during a capacitive sensing period 320. Moreover, theinput device may perform capacitance sensing on multiple electrodeblocks during a single capacitive sensing period 320. For example, thedriver module may drive the necessary sensing cycles 410 on commonelectrodes 0-3 and then drive the necessary sensing cycles on commonelectrodes 4-7 (not shown). Further still, the driver module may alsodrive a voltage on the other common electrodes that are not used forcapacitance sensing during the in-frame blank period 320. That is,instead of permitting the voltage on the other common electrodes (e.g.,common electrode 4 and 5) to float, the driver module may drive a DCvoltage (e.g., a reference voltage) on these electrodes.

In one embodiment, the input device may transmit a transmitter signal onmultiple transmitter electrodes (e.g., sets of common electrodes)simultaneously. Although not shown, the driver module may output adifferent transmitter signal on each transmitter electrode based on amultiplexing schema such as code division multiplexing or orthogonalfrequency division multiplexing. Thus, the embodiments disclosed hereinare not limited to transmitting the same transmitter signal on a subsetof the common electrodes but may transmit different transmitter signalson a plurality of transmitter electrodes simultaneously in order tomeasure the change of capacitance between the transmitter electrodes andthe receiver electrodes. Further, while FIG. 4 illustrates a singlein-frame blanking period, multiple in-frame blanking periods may occurduring a display frame.

In one embodiment, a display frame (refresh) rate is related to thenumber of common electrodes, the length of the row update period, thelength of the in-frame blanking period, and the length of the verticalblanking period. Consider an example where the display device has 800rows (common electrodes) with a row update time 20 ps (pixel updateperiod of 15 ps and a horizontal blanking period of 5 ps) per commonelectrode. Further, in this example, the vertical blanking period is 10rows long, for a total of 810 rows and the in-frame blanking period isessentially 0 ps. Therefore, the display frame rate is 1/(810*20 ps)which is about 60 Hz.

In one embodiment, visual artifacts within a display image due todisplay update interruption may be reduced by varying properties of thein-frame blanking period from display frame to display frame. In someembodiments, the duration of the in-frame blanking periods may vary fromdisplay frame to display frame. In further embodiments, the position ofthe in-frame blanking periods may vary randomly or modulate from displayframe to display frame. For example, the common electrode that is drivenfor display updating before the start of an in-frame blanking period thecommon electrode that is driven row display updating following anin-frame blanking period may change from display frame to display frame.In some embodiments, the duration of in-frame blanking periods may varyindependently from each other. In other embodiments, the position ofin-frame blanking periods may vary independently from each other. Invarious embodiments, the duration of at least two in-frame blankingperiods are varied in the same way: varied in either duration and/orposition. In yet further embodiments, both the duration and position forin-frame blanking periods may vary from display frame to display frame.

Interference Avoidance Through Changing Capacitive Frame Rate

In one embodiment, noise may be mitigated and susceptibility tointerference in touch measurements during capacitive frames may bereduced by varying properties of the non-display update period (e.g.,capacitive sensing period) from display frame to display frame. In someembodiment, the processing system 110 may modify properties of thenon-display update period based on measurements for interference andnoise. In some embodiments, the processing system 110 may change theamount of a non-display update period used for capacitive sensing,change the capacitive frame rate relative to the display frame rate, orsome combination thereof based on interference measurements. Bydynamically decreasing the capacitive frame rate based on interferencemeasurements, the processing system 110 uses additional time to acquiremore samples, which allows for narrower filter bandwidths for filteringresulting signals received on the receiver electrodes. Further, theadditional time afforded by the decrease in capacitive frame rateenables the processing system 110 to increase the range of sensingfrequencies available for frequency hopping and more effectively avoidinterference.

FIG. 5 illustrates a system for communicating between an electronicsystem and an input device that dynamically changes a capacitive framerate relative to a display frame rate, according to one embodimentdisclosed herein. In one embodiment an electronic system 150 is coupledto an input device 100. As mentioned in regards to FIG. 1, theelectronic system 150 broadly refers to any system capable ofelectronically processing information. Some non-limiting examples ofelectronic systems 150 include personal computers of all sizes andshapes, such as desktop computers, laptop computers, netbook computers,tablets, web browsers, e-book readers, and personal digital assistants(PDAs). The electronic system 150 may transmit data, such as displayframes, to the input device 100 for display.

The input device 100, in one embodiment, may be configured to provideinput to an electronic system 150 as well as receive and process displaydata transmitted from the electronic system 150. The input device 100includes a display screen 500 and a processing system 110. The displayscreen 500 includes a plurality of pixels arranged as one or moredisplay lines that are updated based on display frames received from theelectronic system 150.

The processing system 110 is configured to operate the hardware of theinput device 100 to detect input in the sensing region—e.g., someportion of the display screen 500. The processing system 110 comprisesparts of or all of one or more integrated circuits (ICs) and/or othercircuitry components. As shown, the processing system 110 includes atleast a driver module 502, a receiver module 506, and a determinationmodule 504. In one embodiment, the driver module 502 may include drivercircuitry coupled to the plurality of common electrodes 508 of thedisplay screen 500 configured to be driven for display updating andcapacitive sensing. The driver module 502 is configured to drive one ormore of the common electrodes 508 for display updating during displayline update periods (e.g., pixel update periods 315) of a display frame.The driver module 502 may be configured to drive the common electrodes508 such that the display frames occur at a pre-determined display framerate.

In one embodiment, the driver module 502 may be configured to drive oneor more common electrode sets (e.g., transmitter electrode 160) forcapacitive sensing during non-display update periods (e.g., capacitivesensing periods 320). In one embodiment, the determination module 504may configure the timing and duration of the non-display update periodsbased on a capacitive frame rate. In some embodiments, the non-displayupdate periods may occur after a first display line update period andbefore a second display line update period of a display frame. Invarious embodiments, a non-display update period may be at least as longas the first display line update period. In one embodiment, the drivermodule 502 may be configured to operate one or more of the commonelectrodes 508 for interference detection during a non-display updateperiod.

In one embodiment, the receiver module 506 is coupled to a plurality ofreceiver electrodes 170 and configured to receive resulting signals withthe plurality of receiver electrodes 170. In some embodiments, thereceiver module 506 is configured to receive first resulting signalsduring a first non-display period and second resulting signals during asecond non-display period.

In one embodiment, the determination module 504 is configured todetermine an interference measurement based at least in part on thesecond resulting signals. In some embodiments, the determination module504 is configured to adjust the capacitive frame rate relative to thedisplay frame rate based on the interference measurement. In oneembodiment, the determination module 504 may control the driver module502 to change duration and timing of the non-display update periodsbased on the adjusted capacitive frame rate. In one embodiment, thedetermination module 504 may adjust an amount of the first non-displayperiod which is used for capacitive sensing based on the interferencemeasurement. In some embodiments, the determination module 504 isconfigured to adjust a length of the non-display update periods based onthe interference measurement.

In some embodiments, the determination module 504 is configured toadjust the capacitive frame rate relative to the display frame rate, anddrive the first common electrode set for capacitive sensing during athird non-display period of the first display frame, the thirdnon-display period occurring after the first non-display period, thefirst and third non-display periods comprising a capacitive frame. Insome embodiments, the determination module 504 is configured to adjustthe amount of the second non-display period which is used for capacitivesensing by shifting from driving the first common electrode set with afirst transmitter signal having a first frequency to driving the firstcommon electrode set with a second transmitter signal having a secondfrequency, wherein the first frequency is different from the secondfrequency.

FIG. 6 illustrates a method of mitigating noise during capacitancesensing by modifying a capacitive frame rate relative to a display framerate for display updating, according to an embodiment disclosed herein.FIG. 6 illustrates a single implementation, and other implementationsare possible. Further, in other implementations all of the illustrated“states” and processes may not be used. For example, there may not be a“high noise” state in various embodiments. Further the order in whichthe different processes and states may be varied in other embodiments.

The method 600 begins at step 602 with the processing system 110 settingdefault properties for the capacitive frame and the non-display updateperiod used for capacitive sensing, such as a default capacitive framerate. In one embodiment, the capacitive frame rate may be expressedrelative to the display frame rate. For example, the capacitive framerate may be represented by a ratio “R” between the capacitive frameperiod and the display frame period (e.g., R=T_(touch)/T_(display)).

In one embodiment, different baselines may be used for each capacitiveframe rate. Further, in various embodiments, a baseline may be relaxedor adjusted in some other way that it may be used with the differentcapacitive frame rates.

In some embodiments, the default capacitive frame rate can be set at ahighest available value (e.g., as configured by the input device), thelowest available value, or any value in between. In one embodiment, thecapacitive frame rate may be set based on an overall risk ofinterference. For example, if there is a relatively high risk of therebeing a relatively high level of interference, then a lower capacitiveframe rate may be selected (e.g., by reducing the ratio R). However, ifthere is a relatively low risk of there being a relatively high level ofinterference, then a higher capacitive frame rate may be selected.

At step 604, the processing system 110 acquires one or more capacitiveframe. In one embodiment, the driver module drives a set of one or moreof the common electrodes for capacitive sensing during the non-displayupdate period, and the receiver module receives resulting signals fromreceiver electrodes. In various embodiments, multiple common electrodesets may be simultaneously driven with transmitter signals during anon-display update period (e.g., capacitive sensing period), where eachtransmitter signal is based on different ones of a plurality of codes,including code division multiplexing, orthogonal frequency-divisionmultiplexing, pseudorandom codes, Walsh codes, Hadamard codes, Goldcodes, or the like. Further the plurality of codes may be based on anyplurality of codes that are able to provide mathematical independentresults.

At step 606, the processing system 110 estimates interference byacquiring a measurement of interference. An interference measurement maybe acquired using any known method. In one embodiment, processing system110 is configured to operate one or more of the common electrodes forinterference sensing while receiving resulting signals with the receiverelectrodes. A measurement of the interference may then be determinedbased on the resulting signals. Operating the common electrodes forinterference sensing may include electrically floating or driving thecommon electrodes with a substantially constant voltage. In someembodiments, a first capacitive frame or a first set of capacitiveframes (e.g., touch frame(s)) may be acquired and a measure of theinterference may then be determined based on one more of the capacitiveframes.

In various embodiments, the processing system 110 processes the acquiredcapacitive frames. In one embodiment, the processing system 110 modifiesthe capacitive frame rate based on the interference measurement. In someembodiments, the processing system 110 may decrease the capacitive framerate relative to the display frame rate if the interference measurementmeets or exceeds some threshold value. In other embodiments, theprocessing system 110 may increase the capacitive frame rate relativethe display frame rate if the interference measurement does not exceedthe threshold value. As such, at step 610, the processing system 110determines whether the interference measurement (e.g., acquired at step606) meets or exceeds a threshold value. In one embodiment, theprocessing system 110 may further determine to adjust the capacitiveframe rate based on whether the processing system 110 has entered into alogical “high noise” state, which is discussed later.

At step 612, if the estimated interference exceeds a threshold value,the processing system 110 may modify the transmitter signal frequencyused to drive the common electrodes and shift to a different transmittersignal frequency. In one embodiment, the processing system 110 maymodify the amount of the non-display update period which is used forcapacitive sensing based on the interference measurement. By changingthe amount of the non-display update period used for capacitive sensing,the processing system 110 may increase the range of sensing frequenciesavailable for frequency hopping.

In one embodiment, common electrodes are configured to transmit a firsttransmitter signal for capacitive sensing during the non-display updateperiod (e.g., capacitive sensing period), the first transmitter signalhaving a first transmitter frequency. Receiver electrodes 170 receiveresulting signals that comprise effects corresponding to the firsttransmitter signal and a measurement of the interference of the firsttransmitter signal may be acquired based on the resulting signals. Inone embodiment, the processing system 110 is configured to shift fromtransmitting a first transmitter signal having a first frequency totransmitting a second transmitter signal having a second frequencydifferent from the first frequency, based on the measurement ofinterference.

In one embodiment, when the measurement of interference is above athreshold, the processing system 110 is configured to shift fromtransmitting a first transmitter signal having a first frequency totransmitting a second transmitter signal having a second frequency,where the first and second frequencies are different. In yet otherembodiments, the processing system 110 shifts from transmitting a firsttransmitter signal to a second transmitter signal based on themeasurement of interference, where the second transmitter signalcomprises at least one of a different amplitude, phase, polarity,frequency and waveform. The waveform may be one of a square waveform,triangular waveform, sawtooth waveform, sinusoidal waveform, or thelike. A shift to different transmitter signal frequencies is shown ingreater detail in FIG. 7.

In the embodiment of FIG. 7, three different non-display update periods702, 704, 706 (e.g., in-frame blanking periods) are illustrated, whereeach non-display update period is related to a different “gear”. Eachgear represents a different amount of the non-display update period thatis used for capacitive sensing. Further, each gear is related to adifferent transmitter signal frequency that is driven onto a commonelectrode set (e.g., transmitter electrode) for capacitive sensing. Asshown, gear₁ may represent a first transmitter signal frequency, gear₂may represent a second transmitter signal frequency and gear_(last) mayrepresent the last transmitter signal frequency available given theduration of the non-display update period. Further, as is illustrated,the first transmitter signal frequency is higher than the secondtransmitter signal frequency, which are both higher than the lasttransmitter signal frequency.

It should be recognized that the processing system 110 may use less thanall of the time in a non-display update period (e.g., capacitive sensingperiod 320) for capacitive sensing. For example, the processing system110 drives common electrodes for capacitive sensing at a firsttransmitter signal frequency corresponding to gear₁ for an amount(identified as period 710) of the non-display update period 702. Asshown, the processing system 110 drives a plurality of N sensing cyclesduring the period 710; the remainder of the non-display update period702 (identified as period 712) may be unused or reserved for uses otherthan capacitive sensing.

In one embodiment, processing system 110 is configured to adjust anamount of the non-display update period that is used for capacitivesensing based on a measurement of interference. For example, theprocessing system 110 may shift from gear₁ to gear₂ based on ameasurement of the interference. To shift transmitter signalfrequencies, the processing system 110 may use an increased amount ofthe non-display period 704 (identified as period 714) for driving commonelectrodes at a second transmitter signal frequency corresponding togear₂. As shown, in some embodiments, the amount 714 of the non-displayupdate period 704 may be longer than the amount 710 of the non-displayupdate period 702 used for capacitive sensing. Further, processingsystem 110 may shift from gear₂ to gear₁ based on a measurement of theinterference.

Referring back to FIG. 6, when the measurement of interference isdetermined to meet or exceed a threshold amount of interference, theamount of the non-display update period that is used for capacitivesensing is adjusted such that the processing system shifts to differentgear. At step 614, if a “quiet” gear (e.g., a gear that allows theinterference measurement to fall below the threshold level) is found,then the processing system 110 loops to step 604 to acquire at leastanother capacitive frame using that gear. If a “quiet” gear is notfound, the processing system 110 may then determine if the capacitiveframe rate can be adjusted relative to the display frame rate.

At step 616, the processing system 110 first determines whether anadjusted capacitive frame rate is available, for example, if the lowestconfigurable capacitive frame rate is already being used. If there is anavailability to adjust the capacitive frame rate, at step 618, thecapacitive frame rate is adjusted and a “quiet” gear at that adjustedframe rate is found. As such, the processing system 110 may modify acombination of the length of the non-display update period, which isrelated to changing the capacitive frame rate, and the amount of thenon-display update period used for capacitive sensing, which is relatedto changing the transmitter signal frequency, based on the measurementof interference. If there are no available capacitive frame rates toadjust to (e.g., already at a minimum capacitive frame rate accepted bythe processing system 110), at step 624, the processing system 110switches or enters a “high noise” state, which is a logic stateindicating the input device 100 is affected by a relatively high levelnoise and interference. In such a state, in some embodiments, theprocessing system 110 may stop reporting positional information untilthe processing system 110 is determined to be no longer operating in a“high noise” state. In various embodiments, the processing system 110may change any of its operating modes or characteristics, for example,to employ other supplemental techniques for mitigating noise andinterference, until it is determined to be no longer operating in a“high noise” state.

In the embodiment shown, referring back to step 618, the processingsystem 110 decreases the capacitive frame rate relative to the displayframe rate based on the measurement of interference. In one embodiment,decreasing the capacitive frame rate may result in a change in timing ofthe non-display update periods relative to the display frames. In someembodiments, decreasing the capacitive frame rate includes increasingthe length of the non-display update periods (e.g., in-frame blankingperiods) while also decreasing the number of non-display update periodsper display frame. In another embodiment, decreasing the capacitiveframe rate includes switching from driving a common electrode set duringa single non-display period to acquire a capacitive frame to driving thesame common electrode set during multiple non-display update periods(e.g., in-frame blanking periods) to acquire at least a portion of acapacitive frame. In one embodiment, decreasing the capacitive framerate may increase the number of samples acquired while driving a set ofcommon electrodes for capacitive sensing. In one implementation, theprocessing system 110 represents the change in capacitive frame rate bydecreasing the ratio R between the touch frame periods and the displayframe period (e.g., from 2× to 1.5×). By way of example, assuming adisplay frame rate of 60 Hz, the capacitive frame rate may be adjustedbetween 120 Hz (e.g., R=2), to 90 Hz (e.g., R=1.5) to 60 Hz (e.g., R=1)according to interference measurements.

Referring back to step 610, when the measurement of interference isdetermined to not meet or exceed a threshold amount of interference, atstep 620, the processing system 110 determines whether the highestavailable capacitive frame rate is being used. If there are higheravailable capacitive frame rates, at step 622, the processing system 110increases the capacitive frame rate, and proceeds to acquire additionalcapacitive frames (e.g., at step 604). If there are not any higheravailable capacitive frame rates, the processing system 110 continues toacquire additional capacitive frames (e.g., at step 604) at the currentcapacitive frame rate. In some embodiments, as shown in step 620, theprocessing system 110 may further determine to maintain the currentcapacitive frame rate if the capacitive frame rate has been decreasedrecently. By basing an increase of the capacitive frame rate at least inpart on the recent history of the capacitive frame rate, the processingsystem 110 uses the recency of a last decrease as a type of hysteresisloop.

In one embodiment, at step 622, the processing system 110 may increasethe capacitive frame rate relative to the display frame rate based onthe measurement of interference. In some embodiments, increasing thecapacitive frame rate includes decreasing the length of the non-displayupdate periods (e.g., in-frame blanking periods) while also increasingthe number of non-display update periods per display frame. In anotherembodiment, increasing the capacitive frame rate includes switching fromdriving a common electrode set during multiple non-display updateperiods (in-frame blanking periods) to acquire a portion of a capacitiveframe (i.e., a capacitive frame) to driving the same common electrodeset during a single non-display period to acquire a capacitive frame.

In one alternative embodiment of method described in FIG. 6, theprocessing system 110 may have a pre-determined maximum duration for thenon-display update periods (e.g., capacitive sensing period). In such anembodiment, the processing system 110 may vary the amount of non-displayupdate period used for capacitive sensing from shifting gear to gear, asshown in FIG. 7 above, rather than additionally redistributing timebetween display periods and capacitive sensing periods. In someembodiments, the non-display update periods in a display frame may haveequal durations. In various embodiments each gear may have the samenumber of sensing periods or the number of sensing periods may differfrom gear to gear. In some embodiments, the input device may have apre-determined maximum time budget per display frame for the collectionof capacitive measurements, which is selected such that display qualitydoes not suffer, for example, from motion artifacts. In someembodiments, to determine the timing of the non-display update periods,the time budget may be divided by the needed number of non-displayupdate periods per display frame and the ratio R. As described above,the needed number of non-display periods per display frame may becalculated using the expression: R*(N_(TX)+N_(noise)) where N_(TX) is anumber of transmitter electrodes (e.g., common electrode set) percapacitive frame, and N_(noise) is a number of noise bursts percapacitive frame.

In one embodiment, the number of bursts per cluster may be increasedproportionally to the decrease of the capacitive frame rate (e.g., ratioR). For example, switching from a capacitive frame rate of 120 Hz to 60Hz (e.g., R=2 to R=1) may allow twice as many bursts per cluster.Alternatively, in some embodiments, the number of bursts per cluster mayremain the same, in which case, contiguous acquisition of a burst may bebroken (e.g., across display frames). As such, it has been determinedthat in these cases new harmonics in susceptibility to interference mayappear. In yet other embodiments, to minimize motion artifacts,consecutive non-display update periods may be used for data collectionof samples from a same transmitter electrode (e.g., common electrodeset). The use of consecutive non-display update periods may result inincreased separation of harmonics in susceptibility to interference inthe frequency domain.

In another embodiment, the processing system 110 may change the timingof the non-display update periods (e.g., capacitive sensing periods) anddisplay periods (e.g., pixel update periods) based on the modifiedcapacitive frame rate. An example of re-timed non-display update periodsresulting from decreasing the capacitive frame rate (e.g., loweringratio R) is shown in greater detail in FIGS. 8A and 8B.

FIGS. 8A and 8B illustrate timing charts for embodiment where thecapacitive frame rate is adjusted by increasing the length and number ofnon-display update periods. In FIGS. 8A and 8B, non-display updateperiods interleaved with display line update periods are shown for adisplay device 800 configured to drive common electrodes of commonelectrode sets for capacitive sensing (e.g., “TX-segment₁,”“TX-segment₂,” etc.). In one embodiment, non-display update periods(e.g., Non-Display Update₁) are interleaved with display update clusters(e.g., Display Line 1 to Display Line M/2). In the embodiment shown, Ncommon electrode sets are equally sized, each covering M display linesof the display device. However, in other embodiments, one or more of theN common electrode sets may differ in size, where at least one commonelectrode set covers a number of display lines that is different fromthe number covered by another common electrode set. In one embodiment,the common electrodes 0 to M*N sequentially transmit signals for displayupdating during corresponding pixel update periods of common electrodes0-M*N (e.g., Display Line₁₅₁), while during the non-display updateperiods (e.g., Non-Display Update₁) of the display frame, a set of Mcommon electrodes (e.g., TX-segment₁) simultaneously transmit signalsfor capacitive sensing. For sake of discussion, M is assumed to be aneven number, and it may be assumed that noise bursts are notillustrated. While in the embodiment of FIG. 8A each TX-segmentcorresponds to a non-display period and a plurality of display lines, invarious embodiments, multiple TX-segments correspond to the samenon-display period, such that multiple TX-segments may be driven forcapacitive sensing during a common non-display update period. In oneembodiment, multiple TX-segments are simultaneously driven withtransmitter signals based on different ones of a pluralitymathematically independent code during a common non-display updateperiod. In one embodiment, multiple TX-segments are simultaneouslydriven with transmitter signals based on different ones of a pluralitymathematically independent codes during one or more common non-displayupdate periods.

In the timing chart of FIG. 8A, the capacitive frame rate has been setto be 2× the display frame rate. As shown, the non-display updateperiods (e.g., “Non-Display Update₁,” “Non-Display Update_(N)”) have aduration that is at least as long as the display line update periods.Further, the non-display update periods are timed within the displayframe to achieve the desired 2× capacitive frame rate. In oneembodiment, the number of non-display update periods per display framemay be calculated according to the expression R*(N_(TX)+N_(noise)),where the ratio R is set according to the current capacitive frame rate,N_(TX) is a number of transmitter segments (e.g., sets of commonelectrodes), or groups of transmitter segments used in code divisionmultiplexing sensing, per touch frame, and N_(noise) is a number ofnoise bursts per touch frame.

In one example, in a display device having a number of common electrodesets N=5, each covering a number of display lines M=100, the non-displayupdate periods (e.g., “Non-Display Update₁,” “Non-Display Update_(N)”)are timed for a first capacitive frame 802, which may represent everyodd capacitive frame, and a second capacitive frame 804, which mayrepresent every even capacitive frame. In this example, Non-DisplayUpdate₁ to Non-Display Update₅ periods that make up the first capacitiveframe 802 are interleaved with display update clusters Display Line₁ toDisplay Line₅₀ (e.g., generally as, display line 1 to display line M/2),Display Line₅₁ to Display Line₁₀₀ (e.g., display line M/2+1 to displayline M), Display Line₁₀₁ to Display Line₁₅₀ (e.g., generally as, displayline M/2*(i−1)+1 to display line M/2*i), etc. Further, as shown, asecond Non-Display Update₁ corresponding to the same first set of commonelectrodes (e.g., TX-segment₁) is interleaved within another displayline cluster having Display Line₂₅₁ to Display Line₃₀₀ (e.g., generallyas, display line M/2*N+1 to display line M/2*N+M/2) of the same displayframe. As shown, in this example, by the time the last display line 500(e.g., Display Line M*N) is driven for display updating and the displayframe has ended, a non-display update period corresponding to eachcommon electrode set segment has occurred twice. As such, a capacitiveframe rate double that of the display frame rate has been achieved.

In some embodiments, the capacitive frame rate may be decreased relativeto the display frame rate based on a measurement of interference,resulting in a re-timing of the non-display update periods. In thetiming chart of FIG. 8B, the capacitive frame rate has been adjusted byincreasing the length and number of non-display update periods. Itshould be recognized an increase in the capacitive frame rate relativeto the display frame rate may result in a re-timing of the non-displayupdate periods (e.g., from timing chart in FIG. 8B to the timing chartin FIG. 8A).

In the embodiment of FIG. 8B, the capacitive frame rate has beendecreased to be 1× the display frame rate. As shown, the duration of thenon-display update periods (e.g., “Non-Display Update₁,” “Non-DisplayUpdate_(N)”) have been increased to be longer than the display lineupdate periods. While each non-display update period and correspondingnumber of display lines are shown as being equal, in variousembodiments, one or more of the N common electrode sets may differ insize, where at least one common electrode set covers a number of displaylines that is different from the number covered by another commonelectrode set. Further, as is stated above in regards to FIG. 8A,multiple TX-segments may be simultaneously driven during eachnon-display update period. In some embodiments, each burst is acquiredin contiguous periods. In some embodiments, the non-display updateperiods are re-timed within the display frame. Continuing the example ofthe display device where N=5 and M=100, the non-display update periods(e.g., “Non-Display Update₁,” “Non-Display Update_(N)”) which are usedfor capacitive sensing in the capacitive frame 806, are interleaved withdisplay update clusters Display Line₁ to Display Line₁₀₀ (e.g.,generally as, display line 1 to display line M), Display Line₁₀₁ toDisplay Line₂₀₀ (e.g., display line M+1 to display line M*2), DisplayLine₂₀₁ to Display Line₃₀₀ (e.g., generally as, display line M*(i−1)+1to display line M*i), etc. As shown, in this example, by the time thelast display line 500 (e.g., Display Line M*N) is driven for displayupdating and the display frame has ended, a non-display update periodfor each transmitter segment has occurred only once. As such, acapacitive frame rate of 1× the display frame rate has been achieved.

FIG. 9 illustrates timing charts 900A and 900B for capacitive sensingperiods at different capacitive frame rates, according to one embodimentdisclosed herein. As shown in timing chart 900A, three differentnon-display update periods (e.g., in-frame blanking periods) areillustrated, where each non-display update period is related to adifferent gear, similar to the non-display update periods shown in FIG.7. As shown, each gear represents a different amount of the non-displayupdate period that is used for capacitive sensing during N sensingperiods. As is stated above, in various embodiments, the number ofsensing periods may vary from gear to gear.

In the embodiment shown in timing chart 900B, non-display update periodsare re-timed after a decrease in the capacitive frame rate. In oneembodiment, the non-display update periods have been increased inlength, which allows for an increase number of samples to be acquiredper transmitter signal. In some embodiments, a number of samples perburst may be increased proportionally to a decrease in the capacitiveframe rate (e.g., the ratio R). For example, a set of the commonelectrodes may be driven with a transmitter signal having a firsttransmitter signal frequency to acquire 2*N sensing periods, rather thanjust N sensing periods, using the same corresponding gea_(r1). Theincreased number of samples may be used for narrow filter bandwidths,thereby reducing susceptibility to interference during capacitivesensing.

In one embodiment, the non-display update periods have been increased inlength, which allows for an increased amount of the non-display updateperiod to be used for capacitive sensing. In some embodiments,decreasing the capacitive frame rate relative to the display frame ratemay result in an increase in time budget for frequency hopping as well.The increased amount of the non-display update period to be used forcapacitive sensing allows for additional transmitter signal frequenciesthat were unavailable within non-display update periods of the previouscapacitive frame rate. The common electrodes may be driven at adifferent transmitter signal frequency using one of the additional gearsmade available by the increase in the non-display update period. Assuch, changing the capacitive frame rate relative to the display framerate based on the measurement of interference may increase the range ofavailable sensing frequencies for more effective frequency hopping tomore effectively avoid interference. Further, dynamically decreasing thecapacitive frame rate based on interference measurements allows foradditional time to acquire more samples, which enables for narrowerfilter bandwidths for filtering resulting signals received on thereceiver electrodes. As such, by dynamically adjusting the capacitiveframe rate based on interference measurements, embodiments of theinvention are able to balance performance and noise mitigation byincreasing the capacitive frame rate based on detecting relatively lowinterference and decreasing the capacitive frame rate based onrelatively high interference.

In view of the foregoing, the scope of the present disclosure isdetermined by the claims that follow. However, those skilled in the artwill recognize that the foregoing description and examples have beenpresented for the purposes of illustration and example only. Thedescription as set forth is not intended to be exhaustive or to limitthe invention to the precise form disclosed.

1. A processing system, comprising: driver circuitry coupled to aplurality of electrodes configured to be driven for display updating andcapacitive sensing, wherein the driver circuitry is configured to: drivea first electrode for display updating a first display line during afirst display line update period of a first display frame, drive asecond electrode for display updating a second display line during asecond display line update period of the first display frame, and drivea first electrode set comprising at least one of the plurality ofelectrodes to generate a capacitive measurement during a firstnon-display update period of the first display frame, the firstnon-display update period occurring after the first display line updateperiod and before the second display line update period, and the firstnon-display update period being at least as long as the first displayline update period, wherein display updating is paused during the firstnon-display update period; and a determination module configured todetermine an interference measurement based at least in part on thecapacitive measurement generated during the first non-display updateperiod, wherein an amount of a second non-display update period which isused for capacitive sensing is adjusted based on the interferencemeasurement.
 2. The processing system of claim 1, wherein thedetermination module is further configured to adjust a capacitive framerate used during the first non-display update period relative to adisplay frame rate based on the interference measurement.
 3. Theprocessing system of claim 2, wherein the determination moduleconfigured to adjust the capacitive frame rate relative to the displayframe rate is further configured to adjust a length of the firstnon-display period.
 4. The processing system of claim 2, wherein thedetermination module configured to adjust the capacitive frame raterelative to the display frame rate is further configured to drive thefirst electrode set for capacitive sensing during a third non-displayperiod of the first display frame, the third non-display periodoccurring after the first non-display period, the first and thirdnon-display periods comprising a capacitive frame.
 5. The processingsystem of claim 1, wherein the determination module is furtherconfigured to increase the amount of the second non-display period whichis used for capacitive sensing.
 6. The processing system of claim 1,wherein the determination module is further configured to decrease theamount of the second non-display period which is used for capacitivesensing.
 7. The processing system of claim 1, wherein the drivercircuitry is further configured to one of (i) drive the second electrodeset with a substantially constant voltage and (ii) electrically floatthe second electrode set.
 8. The processing system of claim 1, whereinthe determination module is further configured to shift from driving thefirst electrode set with a first transmitter signal having a firstfrequency to driving the first electrode set with a second transmittersignal having a second frequency, wherein the first frequency isdifferent from the second frequency.
 9. A processing system, comprising:driver circuitry coupled to a plurality of electrodes configured to bedriven for display updating and capacitive sensing, wherein the drivercircuitry is configured to: drive a first electrode for display updatingduring a first display line update period of a first display frame,drive a second electrode for display updating during a second displayline update period of the first display frame, and drive a firstelectrode set comprising at least one of the plurality of electrodes togenerate a capacitive measurement during a first non-display period,wherein the first non-display period occurs after the first display lineupdate period and before the second display line update period, and thefirst non-display period being at least as long as the first displayline update period; and a determination module configured to determinean interference measurement the capacitive measurement generated duringthe first non-display update period, wherein the determination module isfurther configured to adjust an amount of capacitive frames per displayframe based on the interference measurement.
 10. The processing systemof claim 9, wherein the determination module is further configured toadjust a length of the first non-display period.
 11. The processingsystem of claim 9, wherein the determination module is furtherconfigured to drive the first electrode set for capacitive sensingduring a second non-display period of the first display frame, thesecond non-display period occurring after the first non-display period,the first and second non-display periods comprising a capacitive frame.12. The processing system of claim 9, wherein the determination moduleis further configured to increase the amount of a second non-displayperiod is used for capacitive sensing.
 13. The processing system ofclaim 9, wherein the driver circuitry is further configured to one of(i) drive the first electrode set with a substantially constant voltageand (ii) electrically float the first electrode set.
 14. The processingsystem of claim 9, wherein the determination module is furtherconfigured to shift from driving the first electrode set with a firsttransmitter signal having a first frequency to driving the firstelectrode set with a second transmitter signal having a secondfrequency, wherein the first frequency is different from the secondfrequency.
 15. A method, comprising: driving, a first electrode of aplurality of electrodes for display updating during a first display lineupdate period of a first display frame, wherein the plurality ofelectrodes are configured for display updating and capacitive sensing;driving a second electrode of the plurality of electrodes for displayupdating during a second display line update period of the first displayframe; performing capacitive sensing using a first electrode setcomprising at least one of the plurality of electrodes to generate aninterference measurement; adjusting an amount of a first non-displayperiod which is used for capacitive sensing based on the interferencemeasurement; and driving a second electrode set comprising at least oneof the plurality of electrodes for capacitive sensing during the firstnon-display period of the first display frame, the first non-displayperiod occurring after the first display line update period and beforethe second display line update period, and the first non-display periodbeing at least as long as the first display line update period.
 16. Themethod of claim 15, wherein performing capacitive sensing using thefirst electrode set to generate the interference measurement comprisesone of driving the first electrode set with a substantially constantvoltage and electrically floating the first electrode set.
 17. Themethod of claim 15, the method further comprising adjusting a capacitiveframe rate relative to a display frame rate based on the interferencedetection.
 18. The method of claim 17, wherein adjusting the capacitiveframe rate relative to the display frame rate comprise one of increasingthe capacitive frame rate relative to the display frame rate anddecreasing the capacitive frame rate relative to the display frame rate.19. The method of claim 15, wherein adjusting the amount of the firstnon-display period which is used for capacitive sensing based on theinterference detection comprises one of increasing the amount of thefirst non-display period which is used for capacitive sensing anddecreasing the amount of the first non-display period which is used forcapacitive sensing.
 20. The method of claim 15, wherein adjusting theamount of the first non-display period which is used for capacitivesensing based on the interference measurement comprises shifting fromdriving the second electrode set with a first transmitter signal havinga first frequency to driving the second electrode set with a secondtransmitter signal having a second frequency, wherein the firstfrequency is different from the second frequency.